According to the Environment Agency, as mass concentration measurement for general atmospheric fine particulate matter PM2.5 is affected by influences such as moisture and semi-volatile organic compounds, it is said that the measurement from the sample by a collection filter is difficult and unresolved.
EPA in the United State and European Union also standardize for measurement methods and present provisions for removing the differences of the data due to influence factors as much as possible.
Besides, also regarding the constituents of PM 2.5, component measurement manuals for ion component, carbon component, metal component and polycyclic aromatic hydrocarbon component are determined, but they have many parts to be developed and necessities to evaluate effectivity and availability of various measuring instruments or the like and to advance the establishment of the measuring methods are described.
Above all, in analyzation of the carbon component, a thermal separation method that has been popular cannot obtain satisfactory accuracy, though thermal separation/heat decomposition correction method is present as a powerful technique, because all analyzers are made by U.S. or European companies, it is described that the population of the analyzing method with the same level of accuracy and sensitivity by promoting the development domestically.
Currently, as PM2.5 flied from the other countries has become the major domestic environmental issues, measures such as installation of measuring instruments in each prefecture and city has become urgent.
A filtering method installed currently is to perform the measurement of mass concentration defined as a standard measuring method for PM2.5 in the United States and European Union. Since atmospheric fine particulate matter gives influence wielding to the atmosphere and enormous influence to the health by entering into the human lungs deeply, so that damage must be prevented by researching the components and derivation of evolution or the like as soon as possible.
Above all, the carbon component is a main component of floating dusts, since the analysis becomes important hint, organic carbon (OC) and elemental carbon (EC) are defined in the seven fractions and measuring conditions. As a measuring method, a heat manganese dioxide oxidation method and a heat separation optics revision method are applied generally, an analyzer that is applied widely on IMPROVE (Interagency Monitoring of Protected Visual Environment) in the United States detects methane reducing CO2 by an FID detector made by DRI and SUNSET.
Calibration line uses 5% methane in helium and 5% carbon in CO2, potassium hydrogen phthalate KHP and Sucrose standard solution for calibration injection. In the case of 5% methane in helium, calibration is performed by injecting volume of 100, 250, 1000, 1500 μL by 1000 μL and 2500 μL syringe. In order to minimize the influence of performance measurement in the FID or electrical drift, concentration calibration in the carbon Analyzer is extremely important.
Furthermore, in the thermal separation that is a mainstream for measurement of carbon component in present atmospheric fine particulate matter, OC (Organic Carbon) and EC (Elemental Carbon) are analyzed fractionally by being liberated from the measurement sample at different temperatures and at an oxidation atmosphere, based on supposition that organic material can be separated by volatilization at low temperature in He stream and that EC cannot be oxidized and separated at the same time, because there is necessity such that the correction for being detected as EC by thermally decomposing and carbonizing the organic material on the process of heating and separation is performed, the thermal separation optical correction method is used mainly. This method was developed in the above-mentioned DRI (Desert Research Institute) in the United State and is a method for correcting by change of reflectivity and transmission of a laser, measurement interference matters such that color in some kind of minerals in soil is changed by heating, that sublimation of the colored organic matters influences to correction by the laser light, that unevenness of the sample on the filter influences to reflection and transmission of light, that a large error in OC value is caused when a carbon fraction peak of the EC1 exceeds 50 μg, or the like, are pointed out.
On the other hand, in Japan, measurement of organic carbon and elemental carbon by an organic elemental analyzer is also attempted and a organic elemental analyzer has been used in research and each measurement institutions for PM2.5, but since this elemental analyzer doesn't have the function such as to accurately separate the organic carbon and inorganic carbon, OC is measured small, EC is measured excessively and detection at low concentration of OC and EC is impossible in this analyzer. Since PM2.5 brings big damage to the health, accurate measurement of PM2.5 is an urgent issue, and it is desired that the development of domestic instruments in order to be popularized widely.